i picked A since the first boldface seems to be a conclusion to me ...
I chose A too. Wouldn't it be a conclusion if I said "Studies have shown that without water life could not be sustained". Lastly, "The study found that.." makes it sound like evidence.
I do see how D could be correct. Can you tell me the source of this question?
Studies have shown that people who keep daily diet records are far more successful at losing weight than people who don’t keep track of what they eat.
Researchers believe that many weight-loss efforts fail because people eat more calories than they intend to consume.
One study followed a group of patients who reported that they could not lose weight when consuming only 1,200 calories a day. The study found that the group consumed, on average, 47% more than it claimed and exercised 51% less.
In contrast, when dieters record what they eat, their actual consumption more closely matches their reported consumption.Therefore, not keeping track of what one eats makes it far more difficult for that person to lose weight.
(A.) The first is a conclusion reached by researchers; the second is evidence that that conclusion is correct.
(D) The first is a premise upon which the researchers base their opinion; the second illustrates that their opinion is correct.
The sentence in red was added by me, to illustrate a possible conclusion of this argument.
(A) When a sentence starts with "studies have shown" it signals a premise. Think of it as building a theory. Your theory is that "keeping track with what you eat helps in losing weight". You need support for this, so you are looking for data that support it. In other words, you would read as many studies as possible and share their results. So, the first sentence, cannot be the actual conclusion. It presents supportive evidence coming from studies. The conclusion, adding up all those premises, could be sth like the sentence in red.
The second sentence cannot be evidence that makes the first statement 100% secure either. That because it is sort of irrelevant. The second sentence only says that the results of one study showed that participants consumed more than ther reported and exercised less that they reported. This doesn't have to do with them keeping records with what they eat, which is what the first sentence says.
(D) is correct. The first is a premise (explained above). The second is another premise in support of the first premise. It adds strength to the first premise in that it shows that people can be misleaded when it comes to how much they have consumed.